This invention relates to apparatus for holding an object example, for holding a work piece on the work holder of a machine tool.
As the method of holding an object on the work table of a machine tool, a mechanical chucking means or magnetic force is usually used. However, these methods suffer disadvantages in that the mechanical chucking means tends to have a complicated structure and to be expensive, whereas the magnetic force method is not applicable when the object to be held is of nonmagnetic material.
In order to overcome these problems, a method has been contrived to hold an object on a work holder by utilizing the vacuum force exerted through a plurality of suction holes formed on the work holder. This method, however, suffers a problem that most of the suction holes remain open after an object is loaded on the work holder, depending on the shape of the object, and air of atmospheric pressure is sucked through such open suction holes, so that only reduced suction force can be exerted on the object to be held.
This invention has been accomplished with a view to solving the problems inherent in the prior art as described above and provides a technique of holding an object, whatever shape it may have, by allowing suction forces to surely act only upon the contact area of the object from those suction holes which are closed by said object and preventing a drop in the suction force therein.